Knee ligament testing device

Claim 1

An apparatus for measuring the relative displacement of the tibia and femur upon application of a force by operator, comprising: a force application arm defining a rigid surface for contacting the lower leg for application of force on the tibia; a reference arm pivotally hinged to said force application arm and defining a rigid surface for contacting the upper leg for application of a force on the femur to counter the force applied to the tibia through the force application arm; means for limiting the force applied to the tibia to a predetermined maximum force to provide reproducibility of displacement measurement and to prevent application of excessive force; a displacement sensor mounted on said reference armhaving an element mounted for movement relative to said reference arm along an axis generally parallel the direction of the displacement of the tibia relative to the femur, one end of the element positioned so as to contact the lower leg in a fixed relation with the tibia at the level of the tibial tubercle; and means for measuring the displacement between the reference arm and the element when the force is applied, the displacement corresponding to the displacement between the femur and tibia.

Claim 2

An apparatus for measuring the relative displacement of the tibia and femur upon application of a force by operator, comprising: a force application arm defining a rigid surface for contacting the lower leg for application of force on the tibia; a reference arm pivotally hinged to said force application arm and defining a rigid surface for contacting the upper leg for application of a force on the femur to counter the force applied to the tibia through the force application arm; means for limiting the force applied to the tibia to a predetermined maximum force to provide reproducibility of displacement measurement and to prevent application of excessive force; a displacement sensor mounted on said reference armhaving an element mounted for movement relative to said reference arm along an axis generally parallel the direction of the displacement of the tibia relative to the femur, one end of the element positioned so as to contact the lower leg in a fixed relation with the tibia at the level of the tibial tubercle; and means for measuring the displacement between the reference arm and the element when the force is applied, the displacement corresponding to the displacement between the femur and tibia.

Claim 8

An apparatus for measuring the relative displacement of the tibia and femur upon application of a force by an operator, comprising: a force application arm defining a rigid surface for contacting the calf of the leg for application of a force on the tibia; a reference arm pivotally hinged to said force application arm, the hinge being positioned below the ankle of the leg being tested when contacted by the surface of the force application arm, said reference arm defining a rigid surface for contacting the upper leg for application of the force on the femur to counter the force applied to the tibia through the force application arm, resulting in a displacement of the tibia relative to the femur; a torque limiter having an input and an output, the force application arm having an aperture formed therein for receiving a portion of the output of the torque limiter, the input of the torque limiter accepting a wrench for application of a torque to the input, the torque limiter limiting the maximum torque at the output independent of the input so that a predetermiend maximum force can be applied through the force application arm to provide reproducibility of displacement measurement and prevent application of excessive force; a movable member mounted on the reference arm for movement generally along the direction of the displacement of the tibia relative to the femur, one end of said member having a pad for contacting the lower leg at the level of the tibial tubercle, application of force on the lower leg through the force application arm resulting in a displacement of the tibia relative to the femur and a corresponding movement of the member relative to the reference arm, said member having first and second posts extending therefrom in a spaced apart relation, the reference arm having structure defining at least one slot generally aligned in the direction of displacement of the tibia relative to the femur, the first and second posts extending through the slot for guiding the member for motion in a plane parallel to the sagittal plane through the midpoint of the knee; a rotary potentiometer mounted on said reference arm, said potentiometer having an input shaft extending between said first and second posts on the member, a strong being secured to said first post, extending to the input shaft of the potentiometer and wrapped thereabout and secured to the second post, motion of the member inducing rotation in the input shaft of the potentiometer; and means for measuring the variation in resistence of the potentiometer from a position before application of force to a position achieved with application of the predetermined maximum force to measure the displacement of the tibia relative to the femur.

Claim 9

An apparatus for measuring the relative displacement of the tibia and femur upon application of a force by an operator, comprising: a force application arm defining a rigid surface for contacting the calf of the leg for application of a force on the tibia; a reference arm pivotally hinged to said force application arm, the hinge being positioned below the ankle of the leg being tested when contacted by the surface of the force application arm, said reference arm defining a rigid surface for contacting the upper leg for application of the force on the femur to counter the force applied to the tibia through the force application arm, resulting in a displacement of the tibia relative to the femur; a torque limiter having an input and an output, the force application arm having an aperture formed therein for receiving a portion of the output of the torque limiter, the input of the torque limiter accepting a wrench for application of a torque to the input, the torque limiter limiting the maximum torque at the output independent of the input so that a predetermiend maximum force can be applied through the force application arm to provide reproducibility of displacement measurement and prevent application of excessive force; a movable member mounted on the reference arm for movement generally along the direction of the displacement of the tibia relative to the femur, one end of said member having a pad for contacting the lower leg at the level of the tibial tubercle, application of force on the lower leg through the force application arm resulting in a displacement of the tibia relative to the femur and a corresponding movement of the member relative to the reference arm, said member having first and second posts extending therefrom in a spaced apart relation, the reference arm having structure defining at least one slot generally aligned in the direction of displacement of the tibia relative to the femur, the first and second posts extending through the slot for guiding the member for motion in a plane parallel to the sagittal plane through the midpoint of the knee; a rotary potentiometer mounted on said reference arm, said potentiometer having an input shaft extending between said first and second posts on the member, a strong being secured to said first post, extending to the input shaft of the potentiometer and wrapped thereabout and secured to the second post, motion of the member inducing rotation in the input shaft of the potentiometer; and means for measuring the variation in resistence of the potentiometer from a position before application of force to a position achieved with application of the predetermined maximum force to measure the displacement of the tibia relative to the femur.

Claim 12

An apparatus for measuring the displacement of the tibia relative to the femur upon application of a force by an operator for testing the ACL ligament in the knee, comprising: a force application arm having a frame and a rigid surface on the top of the frame, the rigid surface for contacting the calf of a leg to be examined to apply a force on the tibia; a reference arm pivotally hinged to said force application arm and comprising a frame, the hinge being located at a greater distance from the knee than the ankle of the patient, said reference arm including a support having a rigid surface at one end for contacting the upper leg at the patella, the opposite end of the support having a surface for application of a force on the patella to counter the force supplied to the tibia through the force application arm; a torque limiter having an input and output, the output being limited to a predetermined maximum torque independent of the torque at the input, the frame of said force application armhaving an aperture for receiving the output of the limiter, application of a torque to the input at least equal to the predetermined maximum torque applying a force on the tibia through the force application arm limited to a predetermined maximum force to provide reproducibility of displacement measurement and to prevent application of excessive force to the leg of the patient; an outer tube fixed relative to the reference arm and having an aperture generally aligned with the direction of displacement of the tibia relative to the femur and centered over the tibial tubercle when the leg of the patient is supported on the force application arm, said outer tube having at least one slot formed therethrough generally extending along the direction of displacement of the tibia and in a plane generally perpendicular to a plane parallel to the sagittal plane through the midpoint of the knee; an inner tube extending into the aperture in said outer tube and confined for movement generally along the direction of displacement of the tibia by the outer tube; said inner tube having means at one end for contacting the lower leg at the level of the tibial tubercle so that the inner tube is movable with the lower leg, said inenr tube having a first and second post extending therefrom through the slot in the outer tube, said slot and posts confining the inner tube to motion within the plane parallel the sagital plane through the midpoint of the knee; a multiturn linear potentiometer mounted on said reference arm adjacent the outer tube, said potentiometer having an input shaft extending between said first and second posts, said potentiometer further having a wiper arm; a string extending between said first and second posts and wrapped about the input shaft of the potentiometer so that linear movement of the inner tube relative to the outer tube is translated into rotary motion of the input shaft of the potentiometer, the displacement of the tibia relative to the femur upon application of force to the tibia resulting in a corresponding rotation of the input shaft of the potentiometer; a voltage source for applying a voltage across the entire resistance of the potentiometer, the input shaft moving the wiper arm, the voltage at the wiper arm therefore corresponding to the displacement of the tibia relative to the femur; means for sensing the voltage at the wiper arm of the potentiometer prior to application of force and at the time of application of the predetermined maximum force and converting the difference in voltage to the displacement; and display means displaying the displacement measured by the means for sensing.

Claim 13

An apparatus for measuring the displacement of the tibia relative to the femur upon application of a force by an operator for testing the ACL ligament in the knee, comprising: a force application arm having a frame and a rigid surface on the top of the frame, the rigid surface for contacting the calf of a leg to be examined to apply a force on the tibia; a reference arm pivotally hinged to said force application arm and comprising a frame, the hinge being located at a greater distance from the knee than the ankle of the patient, said reference arm including a support having a rigid surface at one end for contacting the upper leg at the patella, the opposite end of the support having a surface for application of a force on the patella to counter the force supplied to the tibia through the force application arm; a torque limiter having an input and output, the output being limited to a predetermined maximum torque independent of the torque at the input, the frame of said force application armhaving an aperture for receiving the output of the limiter, application of a torque to the input at least equal to the predetermined maximum torque applying a force on the tibia through the force application arm limited to a predetermined maximum force to provide reproducibility of displacement measurement and to prevent application of excessive force to the leg of the patient; an outer tube fixed relative to the reference arm and having an aperture generally aligned with the direction of displacement of the tibia relative to the femur and centered over the tibial tubercle when the leg of the patient is supported on the force application arm, said outer tube having at least one slot formed therethrough generally extending along the direction of displacement of the tibia and in a plane generally perpendicular to a plane parallel to the sagittal plane through the midpoint of the knee; an inner tube extending into the aperture in said outer tube and confined for movement generally along the direction of displacement of the tibia by the outer tube; said inner tube having means at one end for contacting the lower leg at the level of the tibial tubercle so that the inner tube is movable with the lower leg, said inenr tube having a first and second post extending therefrom through the slot in the outer tube, said slot and posts confining the inner tube to motion within the plane parallel the sagital plane through the midpoint of the knee; a multiturn linear potentiometer mounted on said reference arm adjacent the outer tube, said potentiometer having an input shaft extending between said first and second posts, said potentiometer further having a wiper arm; a string extending between said first and second posts and wrapped about the input shaft of the potentiometer so that linear movement of the inner tube relative to the outer tube is translated into rotary motion of the input shaft of the potentiometer, the displacement of the tibia relative to the femur upon application of force to the tibia resulting in a corresponding rotation of the input shaft of the potentiometer; a voltage source for applying a voltage across the entire resistance of the potentiometer, the input shaft moving the wiper arm, the voltage at the wiper arm therefore corresponding to the displacement of the tibia relative to the femur; means for sensing the voltage at the wiper arm of the potentiometer prior to application of force and at the time of application of the predetermined maximum force and converting the difference in voltage to the displacement; and display means displaying the displacement measured by the means for sensing.